Section 3 of the Mental Health Act: admission for treatment

What is a section 3?

Section 3 authorises admission and detention in hospital for treatment. Use it when the disorder, the essentials of the treatment plan and whether they'd accept informal care are already clear (Code 14.28). It's also the next step for a s2 patient who needs longer.

It lasts up to 6 months at first and can be renewed. It brings two things s2 doesn't: section 117 aftercare, and the option of a CTO.

Section 3 criteria

All four must apply (s3(2)):

• Mental disorder of a nature or degree that makes it appropriate for them to receive medical treatment in hospital.
• Necessity. The treatment is necessary for their health or safety, or to protect others.
• Only in detention. It can't be provided unless they're detained under s3.
• Treatment is available. Appropriate medical treatment is available for them.

A learning disability counts only if it's associated with abnormally aggressive or seriously irresponsible conduct (s1(2A)). Dependence on alcohol or drugs alone isn't a mental disorder (s1(3)). And a mental disorder is never enough by itself (Code 2.6).

Each doctor must give reasons, and say whether other ways of caring for the patient are available and, if so, why they aren't appropriate (s3(3)).

What counts as appropriate medical treatment?

Medical treatment is broad. It includes nursing, psychological intervention and specialist mental health habilitation, rehabilitation and care (s145(1)). Its purpose must be to alleviate, or prevent a worsening of, the disorder or its symptoms or manifestations (s145(4)).

Purpose isn't likelihood. Treatment can be appropriate even if you can't show in advance that it will work (Code 23.4). But it must actually be available in that hospital, not at some point in the future (Code 23.7, 23.10).

The 2025 Act will require a reasonable prospect of therapeutic benefit, and will stop s3 being used for autism or a learning disability alone. Neither is in force (2025 Act ss3, 8).

The nearest relative and section 3

Before applying, the AMHP must consult the nearest relative, unless that isn't reasonably practicable or would involve unreasonable delay (s11(4)(b)). If the nearest relative objects, the AMHP can't apply (s11(4)(a)). Don't avoid consulting just because you expect an objection (Code 14.63).

If they object and detention is still needed, the AMHP can ask the county court to displace them for an unreasonable objection (s29(3)(c), Code 14.65). If the patient is on s2, make that application before the 28 days end, and the s2 continues until the court's decision is final, after any time for appeal (s29(4)). More on the nearest relative.

How long does a section 3 last?

Up to 6 months, beginning with the day of admission. It can then be renewed for 6 months, and after that for a year at a time, with no limit on the number of renewals (s20(1), (2)).

If they were already in hospital, for example on s2, the s3 starts when the application reaches the managers, and the s2 ends (s5(1), s6(4)). The 2025 Act will shorten the periods to 3 months, 3 months, 6 months and then yearly. That isn't in force (2025 Act s29).

How a section 3 is renewed

1. In the last two months of the period, the RC examines the patient (s20(3)).
2. The RC consults one or more other people professionally concerned with the patient's treatment (s20(5)).
3. A second professional from a different profession, involved in the treatment, agrees in writing that the criteria are met. They needn't be an approved clinician (s20(5A), Code 32.6).
4. The RC sends the report on Form H5 to the managers before the current period ends (s20(3)).
5. The managers must review whether to discharge, and the patient can apply to the tribunal again (Code 38.12, s66(1)(f)).

If the second professional doesn't agree, the RC can't renew. Unless the circumstances are exceptional, accept their view and think about discharge (Code 32.9, 32.19). Never let detention carry on past an unrenewed expiry date: that's unlawful (Code 32.10).

Can you refuse treatment on a section 3?

You can refuse, and the refusal should be recorded, but capacity isn't one of the s3 criteria. Part 4 applies. For three months from the first dose in this period of detention, medication for mental disorder can be given under s63 without consent (Code 24.40, 24.41).

After that, s58 needs a certificate. It's Form T2 if the approved clinician certifies that a capable patient consents (s58(3)(a)). It's T3 if a SOAD certifies that the treatment is appropriate for a patient who refuses or lacks capacity (s58(3)(b)).

ECT follows its own rules under s58A (ECT and section 58A). Treatment for a physical illness unrelated to the mental disorder needs consent or the MCA (Code 24.5).

Discharge from section 3

• The RC can discharge at any time by order in writing, and should do so as soon as the criteria are no longer met (s23, Code 32.18).
• The hospital managers can discharge, and the patient can ask them to at any time (s23, Code 38.12).
• The nearest relative can order discharge with 72 hours' written notice. If the RC bars it on M2, the nearest relative is told and can apply to the tribunal within 28 days (s25, s66(1)(g), (2)(d)).
• The tribunal. The patient can apply once in the first 6 months, and once in each renewal period (s66). If there's been no application on the s3, the managers refer the case at 6 months, counted from the start of any s2 before it (s68). They refer again if 3 years pass without a hearing, or 1 year for under-18s.

Section 17 leave isn't discharge. The section stays in force, and the RC can recall them from leave (s17). More on renewal and discharge.

Section 117 aftercare and CTOs

When a s3 patient stops being detained and leaves hospital, the ICB and the local authority must provide or arrange aftercare until both are satisfied it's no longer needed (s117). That includes people on s17 leave or a CTO (Code 33.2). There's no power to charge for it (Reference Guide 29.20).

A s3 patient can be discharged onto a community treatment order, which keeps a power of recall. A s2 patient can't (s17A). More on section 117 aftercare.

Section 3 or something less restrictive?

Put these reasons in the recommendation (s3(3)(b)). MHA or MCA? helps with the choice.

Section 3 and dementia

Dementia is a mental disorder under the Act (Code 2.5), so s3 is possible when the criteria are met. If the person lacks capacity to consent to admission and doesn't object, DoLS or a court order may be available too (Code 13.49). If the MCA can be used safely and effectively, s3 will be hard to justify (Code 14.23).

If they object to admission or to treatment, only the Act is available (Code 13.50, figure 5). AGNI changed what counts as a deprivation of liberty in June 2026, so check DoLS after AGNI.

A worked example

Section 3 fits, because the disorder and the plan are established (Code 14.28). The AMHP consults her husband before applying. The s3 starts when the application reaches the managers, and the s2 ends. Her three-month medication clock still runs from day 2, so a T2 or T3 is due three months after that first dose (Code 25.12). The managers' 6-month tribunal reference counts from her s2 admission (s68(5)).